RT’s New York crew has witnessed NYPD using LRADs, or sound cannons on Occupy Wall Street protesters. Eyewitnesses at the site have tweeted police fired as protesters sang the US national anthem .

­RT correspondent Lucy Kafanov reports that the blasts of sound lasted no more than five seconds, but had a profound effect on protesters.Joshua Paul, an eyewitness, tweeted that LRADs emitted ‘High pitched noise’ and wrote: ‘Natural reaction: My face scrunched and hands started moving to my ears.’